Kidnapping of chicks in emperor penguins: a hormonal by-product?

• Published in: Journal of Experimental Biology
• Main Authors: Angelier, Frédéric, Barbraud, Christophe, Lormée, Hervé, Prud'Homme, François, Chastel, Olivier
• Other Authors: Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Université de La Rochelle (ULR)-Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), Office National de la Chasse et de la Faune Sauvage (ONCFS), ONCFS
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2006
• Subjects: emperor penguin; seabird; prolactin; non-cooperative breeding; kidnapping; hormones; Aptenodytes forsteri; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; [SDE.ES]Environmental Sciences/Environmental and Society; [SDE.MCG]Environmental Sciences/Global Changes; Emperor penguins
• Online Access: https://hal.archives-ouvertes.fr/hal-00182539; https://hal.archives-ouvertes.fr/hal-00182539/document; https://hal.archives-ouvertes.fr/hal-00182539/file/AJEB209.pdf; https://doi.org/10.1242/jeb.02138

International audience The function and causes of kidnapping juveniles are little understood because individuals sustain some breeding costs to rear an unrelated offspring. Here we focus on the proximal causes of this behaviour in emperor penguins (Aptenodytes forsteri), whose failed breeders often kidnap chicks. We experimentally tested the hypothesis that kidnapping behaviour was the result of high residual levels of prolactin (PRL), a hormone involved in parental behaviour. Penguins with artificially decreased PRL levels by bromocriptine administration kidnapped chicks less often than control penguins. Within the bromocriptine treated group, kidnapping behaviour was not totally suppressed and the probability of kidnapping a chick was positively correlated to PRL levels measured before treatment. During breeding, emperor penguins have to forage in remote ice-free areas. In these birds, PRL secretion is poorly influenced by chick stimuli and has probably evolved to maintain a willingness to return to the colony after a long absence at sea. Therefore, penguins that have lost their chick during a foraging trip still maintain high residual PRL levels and this, combined with colonial breeding, probably facilitates kidnapping. We suggest that kidnapping in non-cooperative systems may result from a hormonal byproduct of a reproductive adaptation to extreme conditions.